It is known that one method for treating blood drawn from a patient that is currently performed includes introducing the blood to a cell, which is rotated so that by centrifugal force the blood components are separated according to their different density. In this manner, first plasma, then platelets, and finally red cells pass through the output duct of the cell. To perform separate collection of these components so that they are as pure as possible, i.e., not mixed with the others even in small quantities, it is obviously crucially important to know at all times the composition of the fluid that passes through the cell output duct and it is equally important to identify the moment when the command is to be sent to switch the bag into which the fluid conveyed by the cell output duct is to be directed.
The prior art proposes devices that are not entirely satisfactory, and it is therefore the aim of the present invention to provide a device that provides in an optimum manner the separate collection of the various blood components, particularly platelets, conveyed by the output duct of a blood centrifugation cell.